This invention relates to expansible shafts.
Such shafts have an axially extending housing and a core engager which moves radially from a retracted position within the housing to an expanded position in which the core engager extends beyond the outer housing wall. For example, Peterson U.S. Pat. No. 4,254,920 (assigned to the assignee of this application) discloses a fluid-actuated shaft having an operating rod that is mounted co-axially with and moves axially relative to the housing. Springs move actuators to force the core engagers radially outwardly into engagement with a surrounding core and a fluid-activated piston drives the operating rod in the other direction to retract them. There are also shafts which use mechanical means (e.g., Acme screws) to expand actuators.
Existing shafts are subject to various problems. For example, mechanism coupling the actuator and operating rod may jam or uncouple under high loads, relative rotation of the operating rod and other portions of the shaft may result in movement of the actuating screw, and misalignment of various moving parts in the shaft may cause wear and other operating difficulties.
It is desirable that the shaft should have a high load-carrying capacity; and also that the load capacity should not be adversely affected by flexing of the shaft under load.